FIELD OF THE INVENTION
The invention relates to a process for the production of a waveguide beam converter according to the preamble of claim The process according to the invention is used, in particular, for the production of a waveguide beam converter for increasing the radiation density of a laser beam collection emitted by a linear array of laser diodes.
Individual semiconductor laser diodes are known to represent radiation sources with high radiation density. For physical reasons, however, substantial limitations are found for semiconductor-laser radiation sources with high radiation power. This is because laser diodes output individual laser beams in the form of stripes, so that in order to produce a compact laser beam collection with high radiation power, the striped individual laser beams need to be arranged above one another. However, the high power loss from semiconductor laser diodes places a limitation on the packing density of individual laser diodes. It is therefore necessary for the individual laser beams emitted by a plurality of individual laser diodes to be concentrated, for example using a waveguide beam converter.
A waveguide beam converter of this type is, for example, disclosed by international patent application WO 94/152 34. This document describes a fiber-optic arrangement made up of a plurality of curved rectangular optical fibers, by means of which an input laser beam collection which is emitted by a linear array of laser diodes and consists of individual laser beams arranged next to one another, is converted into an output laser beam connection made up of striped individual laser beams arranged above one another. At their input, the optical fibers are arranged next to one another in a line, so that each individual laser beam of the input laser beam collection is injected into a separate optical fiber. At their output, the optical fibers are arranged above one another in the form of a stack, so that an output laser beam collection of rectangular cross section is emitted from the end faces of the optical fibers. This output laser beam collection is subsequently injected through a spherical lens into a fiber laser of circular cross section.
At their input, the optical fibers are fastened in precision grooves in an alignment block, these being designed in such a way that the arrangement and spacing of the optical fibers with respect to one another corresponds to the arrangement and spacing of the individual laser beams injected. The optical fibers are made of silicate glasses containing alkali metals or alkaline earth metals (soft glass), for example BAK 5 for the fiber core and BAK 2 for the fiber cladding, which is in turn enclosed by a supporting clad made, for example, of LAKN 12. The fiber-optic bundle is produced by the following steps:
Firstly, the fiber core with the fiber cladding is produced. Subsequently, the fiber cladding is covered with the material of the support clad, which has a significantly higher etching rate than the material of the fiber cladding. Before the material of the support clad is subsequently etched off down to a thin support clad layer, the above-described composite made up of the fiber core, fiber cladding and support clad layer is drawn in such a way that, after drawing, the cross section of the fiber core is still somewhat greater than the intended final size.
A number of optical fibers produced in this way are then stacked on one another and connected to one another. The stack is then once more provided with a jacket and then again drawn until the stack has the desired geometry. The optical fibers in the stack are subsequently separated at one end of the stack by etching, fastened next to one another in the precision grooves of the alignment block and formed in such a way that individual laser beams emitted from the linear array of laser diodes can be injected into the ends of the fibers.
As can be seen from the description above, the production of a waveguide beam converter of the type mentioned in the introduction is currently elaborate and complicated, and therefore very cost-intensive.